Steering control with variable damper assistance and method implementing the same

ABSTRACT

One aspect of the present invention regards an automotive steering wheel control system having a steering wheel, a magnetorheological damper in communication with the steering wheel and a road wheel system operably connected to the magnetorheological damper where the magnetorheological damper controls the steering wheel in response to a signal from the road wheel system.

BACKGROUND OF THE INVENTION

[0001] 1. Field Of Invention

[0002] The present invention relates generally to a steering system fora vehicle and more particularly to steering control with variable damperassistance for a steer-by-wire steering system.

[0003] 2. Discussion Of Related Art

[0004] In a steer-by-wire system, the mechanical linkage betweensteering wheel and road wheels has been eliminated. The steering wheelangle command signal (designated as driver input) is translated to aroad wheel angle by using electric analog or digital signals.

[0005] Even though the mechanical linkage between the steering wheel andthe road wheels has been eliminated, a steer-by-wire steering system isexpected not only to produce the same functions and steering feel as aconventional mechanically linked steering system, but it is alsoexpected to implement advance steering system features. Such a steeringsystem is disclosed in U.S. patent Ser. No. 09/808259 the entire contentof which is incorporated herein by reference. Requirements forconventional steering functions and advanced steering features such asadjustable steering feel can be implemented by an advance control systemdesign.

[0006] A steer-by-wire control system must satisfy high quality steeringrequirements and functions, such as a vehicle directional controlrequirement, a steering wheel to road wheel synchronization requirement,adjustable steering effort functions, stability and adjustablereturnability functions, capturing a driver's intent, and adjustablesteering feel functions. On the other hand, the resultant control systemstructure and control strategy must satisfy closed-loop feedback controlsystem requirements and specifications, such as maintaining stability inthe face of uncertainties, rejecting disturbance performance, and quicktime response performance.

BRIEF SUMMARY OF THE INVENTION

[0007] One aspect of the present invention regards an automotivesteering wheel control system having a steering wheel, amagnetorheological damper in communication with the steering wheel and aroad wheel system operably connected to the magnetorheological damper,wherein the magnetorheological damper controls the steering wheel inresponse to the magnetorheological damper receiving a signal from theroad wheel system.

[0008] Another aspect of the present invention regards a steeringlock-to-lock apparatus having a steering apparatus, a switch incommunication with the steering apparatus and a magnetorheologicaldamper responsive to the switch, wherein when the switch is in a lockstate the magnetorheological damper locks the steering apparatus.

[0009] Another aspect of the present invention regards amagnetorheological damper control for an automotive steering controlsystem having a motor amplifier receiving a reference signal andgenerating a motor torque signal, a motor receiving an effective torquesignal based on the sum of a magnetorheological torque signal, a driveraction torque signal and the motor torque signal. The motor generates aroad wheel rate signal based on the effective torque signal. Amagnetorheological damper receives the road wheel rate signal and anamplified control signal from a magnetorheological amplifier. Themagnetorheological amplifier receives a control input signal andgenerates the amplified control signal based on the control inputsignal. The magnetorheological damper generates the magnetorheologicaltorque signal and an integrator that receives the road wheel rate signaland generates a road wheel angle signal.

[0010] Another aspect of the present invention regards a steering wheelcontrol system for a vehicle comprising a first control subsystem havinga magnetorheological damper, a steering wheel motor responsive to acontrolled input torque signal, wherein the first control subsystemgenerates a steering wheel rate signal. The steering wheel controlsystem also has a second control subsystem having a position loopcompensator, a gain adjustable function element responsive to an outputfrom the position loop compensator, a motor amplifier that receives anreference signal from the gain adjustable function element and generatesa motor torque and an integrator that receives the steering wheel ratesignal from the first control subsystem, wherein the second controlsubsystem generates a steering wheel angle signal and a third controlsubsystem having a steering ratio function element and a road wheelcontrol subsystem. The steering ratio function element receives thesteering wheel angle signal and generates a road wheel reference anglesignal. The road wheel subsystem receives the road wheel reference anglesignal and generates a road wheel measurement torque signal.

[0011] Another aspect of the present invention regards a method ofimproving steering feel in an automotive steer-by-wire control system bysensing a steering wheel angle, sensing a road wheel dynamic,controlling a magnetorheological damper in response to the steeringwheel angle and the road wheel dynamic and controlling steering feel inresponse to the magnetorheological damper.

[0012] Another aspect of the present invention regards a method oflocking a steering system by producing a steering apparatus position,controlling a magnetorheological damper in response to the apparatusposition and locking the steering apparatus in response to themagnetorheological damper.

[0013] All of the above aspects of the present invention provide theadvantages of providing an energy efficient adjustable steering feel forthe driver while reducing the energy consumption and decreasing thepackage and cost of the steering system.

[0014] Additional embodiments and advantages of the present inventionwill become apparent from the following description and the appendedclaims when considered with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]FIG. 1 shows a block diagram of an embodiment of a steering wheelcontrol system with a magnetorheological (MR) damper in accordance withthe present invention;

[0016]FIG. 2 shows a block diagram for an embodiment of the MR-dampercontrol portion in accordance with the present invention;

[0017]FIG. 3 shows a block diagram of an embodiment of a variableMR-damper model of a motor-based system, according to the presentinvention;

[0018]FIG. 4 shows a block diagram of another embodiment a steeringwheel control system in accordance with the present invention;

[0019]FIG. 5 shows a block diagram of an embodiment of a lock-to-lockapparatus in accordance with the present invention; and

[0020]FIG. 6 shows curves of MR friction force vs. velocity of theMR-damper in accordance with the present invention;

DETAILED DESCRIPTION OF THE INVENTION

[0021]FIG. 1 shows a block diagram of an embodiment of a steering wheelcontrol system 100 with a magnetorheological (MR) damper 110. Thesteering wheel control system 100 includes a steering apparatus such assteering wheel 111, a road wheel system 112 and the MR-damper 110. Thesteering wheel 111 is in communication with the MR-damper 110. TheMR-damper 110 is operably connected to the road wheel system 112, suchthat the MR-damper 110 controls the steering wheel 111 in response to asignal from the road wheel system 112.

[0022] In the present invention, the steering wheel 111 is connected toa steering wheel angle sensor 113, which senses a steering wheel angleor position and produces a steering wheel angle or position signal θ,117. The steering wheel 111 is typically an automotive steering wheel;however, the steering wheel 111 can be a joystick, a button or the like.The sensor 113 is typically a rotary position sensor; however, anyrotational displacement sensor that meets performance requirements canbe used. For example, potentiometer, optical, encoders and resolvers maybe used for sensor 113.

[0023] A steering wheel unit includes the steering wheel 111, thesteering wheel angle sensor 113, the MR-damper 110, a motor 114 and arotating shaft 115 to connect them. A steering wheel controller 116 isincluded in steering wheel control system 100. Many differentembodiments of controller architectures are possible for the presentinvention. The control task can be executed by a simple constant orproportional controller, and it could take the form of many other typesincluding nonlinear, variable gain, gain scheduling, or any other typeof controller, such as the controllers disclosed in U.S. patentapplication Ser. No. 09/808,259 and U.S. patent Ser. No. ______ entitledVehicle Road Wheel Fuzzy Logic Control System And Method Of ImplementingA Fuzzy Logic Strategy For Same, Brinks, Hofer, Gilson & Lione docketnumber 10541-38, Visteon Corp. docket number V200-0473 and filedconcurrently with the present invention the entire contents of each ofwhich is incorporated herein. The inputs to the steering wheelcontroller 116 are the steering wheel angle signal θ_(s) 117, a steeringwheel reference angle signal θ_(sr) 118 and a road wheel torque signalτ_(r) 119. The outputs of the steering wheel controller are a controlinput torque signal 120 to the motor 114 (via motor amplifier 122), acontrol input torque signal 121 to the MR-damper 110 (via MR amplifier123) and a road wheel reference angle signal θ_(rs) 122 to the roadwheel control system 112. A further explanation of the foregoingcomponents follows.

[0024] The MR-damper 110 uses magnetorheological fluid.Magnetorheological fluid is a type of oil with microscopic ferrousparticles suspended in it. This fluid is a fundamental part of thetechnology in an MR-damper, which is a rotational damping device thatuses MR fluid to achieve its damping characteristics. Such a MR-damper110 is disclosed at web site hftp://www.rheonetic.com as pf the date offiling of the present invention and is made by Lord Corporation, 406Gregson Drive, Cary, N.C. 27511.

[0025] The MR-damper 110 improves steering feel by contributing a verysmooth viscous torque to the steering effort experience by the driverthrough the steering wheel 111. This torque, transmitted by shaft 115,is not only very smooth in nature but is also very fast in responsetime, which makes it ideal for inclusion in an electronically controlledsteering system that is reacting in real time to the always changingdriving environment. The fact that the torque generated by the MR-damper110 is a damping force also provides stability to the steering wheelsystem—this physical reaction is beneficial in eliminating vibrationsand overshoot.

[0026] The MR-damper 110 helps save energy because it is highlyefficient torque generating device. Torque can be generated using lessenergy with the MR-damper 110 than with a motor. Therefore, by utilizingthe MR-damper 110 when possible instead of a steering feedback motor,energy savings are realized, which ultimately results in improved fueleconomy.

[0027] The MR amplifier 123 is an electronic circuit that takes as inputa digital signal (MR-damper control input 121) from the steering wheelcontroller 116 and produces as output an electric signal whose voltageand current power the MR-damper 110 to produce the desired level oftorque to provide steering feel to a driver including locking thesteering wheel 111.

[0028] The motor 114 uses a DC brushed motor, but virtually any motorcan be used as long as it meets the motor's performance requirements(size, weight, cost, torque output, efficiency, etc).

[0029] The motor amplifier 124 is an electronic circuit that takes asinput a digital signal (Motor control input 120) from the steering wheelcontroller 116 and produces as output an electric signal whose voltageand current power the motor 114 to produce the desired level of torque.

[0030] The basic function of the road wheel system 112 is to guarantee aroad wheel angle output signal θ_(r) (FIG. 4) will accurately track thesteering wheel angle reference signal θ_(sr). A road wheel disturbancetorque τ_(F) is also an important input signal. The road wheeldisturbance torque τ_(F) changes with the road conditions, vehicleloads, road-tire friction, vehicle dynamics and external circumstances.The road wheel torque signal τ_(r) is an output of the road wheel system112. The road wheel torque signalτ_(r) can influence the road wheeldisturbance torque signal τ_(F).

[0031]FIG. 2 shows a block diagram for an embodiment of the MR-dampercontrol portion of the present invention. The MR-damper control portionincludes the motor amplifier 124, the motor 114 (along with its load),the MR-damper 110, the MR amplifier 123 and an integrator 210.

[0032] A control structure with a rotary MR-damper 110 is given in FIG.2 that is a development for a motor-based steering control system 100with MR-damper 110 assistance. Based on this realization for a MR-damper110 in the steering control system 100, curves of MR friction force vs.velocity may be obtained by a series of experiments, as shown in FIG. 6.As a result, a model of the rotary MR-damper 110 may be determined asdescribed below.

[0033] In FIG. 2, the signal i _(ref) represents an input referencesignal from the steering wheel controller 116 to the motor amplifier124. The motor amplifier 124 generates a motor torque signal τ_(m). Themotor torque signal τ_(m) is then presented to summing junction 211where it is added to an MR torque signal τ_(mr), which is generated bythe MR damper 110 resulting in the torque signal τ_(c).

[0034] From FIG. 2, the following equation gives the relationship amongthe motor 114, MR-damper 110 and their control variables:

τ_(c)=τ_(m)+τ_(mr)  (1)

[0035] where, as stated above, the torque signal τ_(c) is the sum of themotor amplifier 124 output torque signal τ_(m) and MR torque signalτ_(mr). It is noted that τ_(m) is produced by negative feedback with themotor power amplifier 124, as shown in FIG. 4.

[0036] When the driver turns the steering wheel 111, a disturbancetorque signal τ_(d) is given to the steering control system 100. Thetorque signal τ_(d) can be regarded as a disturbance torque to thefeedback control system. The effective input torque signal to the motor114 is represented as τ_(e). Because the motor 114, the MR-damper 110and the sensor 113 are connected to the same shaft, the driver holdingthe steering wheel will feel the change of this effective torque signalτ_(e).

[0037] The output of the motor 114 is a road wheel rate signal ω_(s).The road wheel rate signal ω_(s). is presented to integrator 210generating a road wheel angle signal θ_(s). The road wheel rate signalω_(s) also serves as an input signal to the MR-damper 110. The MR-damper110 also receives an input from the MR amplifier 123. The MR amplifier123 receives as input a reference signal i_(ref-mr) from the steeringwheel controller 116. The signal i_(ref-mr) represents the MR-damper 110input control signal. The MR torque signal τ_(mr) will change withsignal i_(ref-mr) as shown in FIG. 6.

[0038]FIG. 3 shows a block diagram of a variable MR-damper model of amotor-based system, according to the present invention. The blockdiagram gives a transfer function description for a variable MR-damper110 model of a motor-based system.

[0039] A method of improving steering feel in an automotivesteer-by-wire control system can be expressed by using the followingsteps:

[0040] sensing a steering wheel angle, such as described above in usingsensor 113;

[0041] sensing a road wheel dynamic, such as a road wheel torque;

[0042] controlling an MR-damper in response to a steering wheel angleand the road wheel dynamic. controlling the steering feel in response tothe MR-damper; and

[0043] providing a road wheel angle to a road wheel system as a functionof controlling the MR-damper and the steering feel.

[0044] The road wheel angle can be repetitively calculated in a computerand provided to the road wheel system base on the following controlledplant model: $\begin{matrix}{{\theta_{s}(s)} = {{\frac{M(s)}{s\left( {1 + {{M(s)}{N\left( {\omega {,\quad}\quad i_{{ref} - {mr}}} \right)}}} \right)}{\tau_{d}(s)}} - {\frac{K_{amp}{M(s)}}{s\left( {1 + {{M(s)}{N\left( {\omega {,\quad}\quad i_{{ref} - {mr}}} \right)}}} \right)}{i_{ref}(s)}}}} & (4)\end{matrix}$

[0045] where M(s) represents a transfer function of a motor of thesteering wheel 111 and an assembly of the steering wheel motor, K_(amp)represents a gain of a motor amplifier, i_(ref-mr) represents the inputcontrol signal to the MR-damper, i_(ref) represents the input referencesignal, s represents a complex variable of any given point in afrequency domain, ω represents a rotary rate of the MR-damper, τ_(d)represents a driver torque and N(ω,i_(ref-mr)) represents a non-lineartransfer function of the MR-damper.

[0046] If there is no MR-damper 110, N(ω,i_(ref-mr))=0, then$\begin{matrix}{{\theta_{s}(s)} = {{\frac{M(s)}{s}{\tau_{d}(s)}} - {\frac{K_{amp}{M(s)}}{s}{i_{ref}(s)}}}} & (5)\end{matrix}$

[0047] The MR-damper 110 provides the damping function for the steeringwheel control system 100. As a result, the stability of the steeringwheel control system is improved. The controlled plant model as definedin equation (4) with MR-damper 110 in the motor-based system gives therelationship among the variables and dynamic characteristics.

[0048] As shown in FIG. 3, N(ω,i_(ref-mr)) takes as input ω_(s) (therotational velocity of the motor/MR-damper/steering assembly) andi_(ref-mr) (the current provided by the MR amplifier 123 to drive theMR-damper 110) and produces as output τ_(mr) (the torque of theMR-damper 110). N((ω,i_(ref-mr)) is therefore a nonlinear transferfunction that represents the functional input/output characteristics ofthe MR-damper 110. The characteristics of the transfer function aredetermined experimentally and are based on the physical characteristicsof the MR-damper 100 A representative curve is shown in FIG. 6, wherethe output-input characteristic of MR-damper 110 are(ω_(m3)>ω_(m2)>ω_(m1)) and the rotary rate of the MR-damper 110 isω_(mr) (i=1, 2, . . . n) and the output torque damper is τ_(mr) and theinput current control signal of the MR-damper 110 is i_(ref-mr)

[0049]FIG. 4 shows a block diagram of another embodiment a steeringwheel control system 100 of the present invention. The steering wheelcontrol system 100 is based on the control structure described in U.S.patent Ser. No. 09/808,259 the entire contents of which is incorporatedherein by reference. In the present invention, the MR-damper 100 hasbeen added.

[0050] The steering wheel control system 400, as shown in FIG. 4,includes a steering wheel feedback control system 412, a MR assistedcontrol 413, a steering ratio function element 414 and a road wheelfeedback control subsystem 415. The steering wheel feedback controlsystem 412 includes a position loop compensator 416, which receives thedifference between a steering wheel reference angle signal θ_(sr) and asteering wheel angle θ_(s). The steering wheel reference angle θ_(sr)comes from a position sensor measuring a road wheel angle θ_(r) from theroad wheel feedback control subsystem 415.

[0051] The output of the position loop compensator 416 is received by again adjustable function element 417. The gain adjustable functionelement 417 also receives a road wheel torque signal τ_(T). The roadwheel torque signal τ_(T) is a scaled road wheel torque signal τ_(R)from the road wheel feedback control subsystem 415. The gain adjustablefunction element 417 provides an input reference signal i_(ref) to motoramplifier 124 that generates a motor torque τ_(m) to the MR assistedcontrol 413. The MR assisted control 413 generates a steering wheel ratesignal ω_(s) as an input to an integrator 210. The integrator 210generates the steering wheel angle signal θ_(s), which is fed back tothe position loop compensator 416 and is used as an input to thesteering ratio function element 414. The output of the steering ratiofunction 414 element is a road wheel reference angle θ_(rs). Thesteering ration function 414 adjusts the steering wheel angle θ_(s)based on some calculations to account for steering ratio and otherfactors and then is used as road wheel reference angle θ_(rs).

[0052] In general, the steering wheel angle θ_(s) and the road wheelangle θ_(r) need to stay in alignment with each other. These tworeference angles keep the steering and road wheel angles in proportionalrelationship to each other. The MR assisted control 413 will now bedescribed.

[0053] The MR assisted control 413 includes a MR Control compensator418, a motor 114, an MR amplifier 123 and a MR damper 110. The motortorque signal τ_(m) is presented to summing junction 211 where it isadded to a MR torque signal τ_(mr), which is generated by the MR damper110 resulting in the torque signal τ_(c). It is noted that τ_(m) isproduced by negative feedback with the motor power amplifier 124.

[0054] A torque signal τ_(d) comes from the driver's input, typically bythe driver turning the steering wheel 111. The torque signal τ_(d) canbe regarded as a disturbance torque to the feedback control system. Theeffective input torque signal to the motor 114 is represented as τ_(e).The driver holding the steering wheel will feel the change of thiseffective torque signal τ_(e).

[0055] The output of the motor 114 is the steering wheel rate signalω_(s). The steering wheel rate signal ω_(s) is presented to integrator210 generating a steering wheel angle signal θ_(s), as described above.The steering wheel rate signal ω_(s) also serves as an input signal tothe MR-damper 110. The MR-damper 110 also receives an input from the MRamplifier 123. The MR amplifier 123 receives as input a reference signali_(ref-mr). The signal i_(ref-mr) represents the MR-damper 110 inputcontrol signal. The MR torque signal τ_(mr) will change with signali_(ref-mr).

[0056] The motor 114 will rotate if τ_(e) is not equal to zero. If τ_(e)is equal to τ_(d), the effective torque τ_(e) will be zero and the motor114 will stop rotating. Thus, the driver can feel any significant changein the effective torque τ_(e). Therefore, when the driver releases thesteering wheel 111, the MR torque signal τ_(mr) will be reduced quicklybecause its input signal i_(ref-mr), will rapidly reduce to zero or acertain value. Thus, less energy is spent to affect the returnability ofthe steering wheel 111.

[0057] The MR-damper 110 input signal i_(ref-mr) is connected to theoutput of the MR control compensator 418. The MR control compensatorreceives as input the road wheel torque signal τ_(R) from the road wheelfeedback control subsystem 415. Thus, the MR-damper 110 input signali_(ref-mr) and the resulting MR torque signal τ_(mr) changesproportionally with the road wheel torque value. The MR controlcompensator can be designed as a constant gain compensator, a nonlinearfunction with fixed input and output characteristics or a variable gaincompensator varying with a gain scheduling signal.

[0058] The road wheel feedback control subsystem 415 also receives as aninput a road wheel disturbance torque τ_(F) (due to hitting a bump inthe road, for instance). As stated above, the road wheel disturbancetorque signal τ_(F). is an important input signal. The road wheeldisturbance torque signal τ_(F) changes with the road conditions,vehicle loads, road-tire friction, vehicle dynamics and other externalcircumstances. The road wheel torque τ_(r) can influence the road wheeldisturbance torque signal τ_(F).

[0059]FIG. 5 shows a block diagram of a lock-to-lock apparatus asanother embodiment of the present invention. The lock-to-lock apparatus500 includes a steering apparatus 111, a switch 501 in communicationwith the steering apparatus, an MR amplifier 123, an MR controlcompensator 418, a high gain compensator 502, a comparator 503 and aMR-damper 110, such that when the switch is in a lock state theMR-damper 110 locks the steering apparatus. The lock-to-lock apparatus500 will now be described in detail.

[0060] Comparator 503 receives the absolute value of a steering wheelangle signal θ_(s). The steering wheel angle signal θ_(s) comes from aposition sensor (not shown), which is connected to the steeringapparatus. The steering apparatus can be a steering wheel, a joystick, abutton or the like. The comparator 503 determines if the steering wheelangle signal θ_(s) is less than a predetermined value α. If the absolutevalue of the steering wheel angle signal θ_(s) is less than apredetermined value α, such as |α|=720 degrees, a control line 504places the switch 501 in an ×1 position otherwise the switch 501 isplaced in an ×2 position.

[0061] Switch 501 has two inputs corresponding to the ×1 and ×2positions and an output 505. The ×1 input is connected to the MR controlcompensator 418. The MR control compensator 418 receives the absolutevalue of a road wheel torque signal τ_(R). Typically, the road wheeltorque signal τ_(R) comes from a road wheel system. The MR controlcompensator can be designed as a constant gain compensator, a nonlinearfunction with fixed input and output characteristics or a variable gaincompensator varying with a gain scheduling signal. The ×2 input isconnected to the high gain compensator K_(MT) 502 and it also receivesthe road wheel torque signal τ_(R). The high gain compensator K_(MT) 502produces enough output torque to lock the steering apparatus 111(K_(MT)>>K_(T), where K_(T) is the normal factor value between the roadwheel torque signal and the MR-damper 110 input).

[0062] The output 505 of switch 501 is connected to the input of the MRamplifier 123. The MR-damper 110 receives the output of MR amplifier 123and generates a MR torque signal τ_(mr).

[0063] In the present invention, when the steering wheel angle θ_(s) isless than the predetermined value the road wheel torque signal τ_(R)will pass through the MR control compensator 418 and to the MR-damper110 and driver can move the steering apparatus, as describe above. Ifthe steering wheel angle signal θ_(s) is greater than or equal to thepredetermined value the road wheel torque signal τ_(R) will pass throughthe high gain compensator 502 to the MR-damper 110 and produce asufficiently large output torque to lock the steering apparatus.

[0064] In effect, this feature makes the steering apparatus hard to movein order to communicate to the driver that the road wheels have reachedtheir maximum travel and cannot turn any more in that direction. Thisfeature emulates the mechanical stop feature found on today's steeringsystems.

[0065] The foregoing detailed description is merely illustrative ofseveral physical embodiments of the invention. Physical variations ofthe invention, not fully described in the specification, may beencompassed within the purview of the claims. Accordingly, any narrowerdescription of the elements in the specification should be used forgeneral guidance, rather than to unduly restrict any broaderdescriptions of the elements in the following claims.

We claim:
 1. An automotive steering wheel control system, comprising: asteering wheel; a magnetorheological damper in communication with saidsteering wheel; and a road wheel system operably connected to saidmagnetorheological damper; wherein said magnetorheological dampercontrols said steering wheel in response to said magnetorheologicaldamper receiving a signal from said road wheel system.
 2. The automotivesteering wheel control system of claim 1, further comprising a sensor;said sensor in communication with said magnetorheological damper; andsaid sensor sensing a steering wheel angle from said steering wheel;wherein said sensor generates a steering wheel angle signal based onsaid sensed steering wheel angle.
 3. The automotive steering wheelcontrol system of claim 2, further comprising a steering wheelcontroller that receives said steering wheel angle signal from saidsensor.
 4. The automotive steering wheel control system of claim 3,wherein said steering wheel controller receives a road wheel torquesignal from said road wheel system.
 5. The automotive steering wheelcontrol system of claim 3, wherein said steering wheel controllerreceives a steering wheel reference angle signal from said road wheelsystem.
 6. The automotive steering wheel control system of claim 3,wherein said road wheel system receives a road wheel reference anglesignal from said steering wheel controller.
 7. The automotive steeringwheel control system of claim 3, further comprising a magnetorheologicalamplifier that amplifies a damper control signal from said steeringwheel controller and provides said amplified damper control signal tosaid magnetorheological damper.
 8. The automotive steering wheel controlsystem of claim 3, further comprising: a motor in communication withsaid magnetorheological damper; and a motor amplifier that receives amotor control signal from said steering wheel controller and provides anamplified motor control signal to said motor.
 9. The automotive steeringwheel control system of claim 8, wherein said motor, saidmagnetorheological damper, said sensor and said steering wheel areconnected to one another by a shaft.
 10. The automotive steering wheelcontrol system of claim 9, wherein said shaft rotates.
 11. A steeringlock-to-lock apparatus, comprising: a steering apparatus; a switch incommunication with said steering apparatus; and a magnetorheologicaldamper responsive to said switch; wherein when said switch is in a lockstate said magnetorheological damper locks said steering apparatus. 12.The steering lock-to-lock apparatus of claim 11 wherein said steeringapparatus is a steering wheel.
 13. The steering lock-to-lock apparatusof claim 11 wherein said steering apparatus is a joystick.
 14. Thesteering lock-to-lock apparatus of claim 11 wherein said steeringapparatus is a button.
 15. The steering lock-to-lock apparatus of claim11 further comprising: a control compensator connected to an input ofsaid switch; said control compensator receives a signal corresponding toan absolute value of a road wheel torque signal when said switch isconnected to said input.
 16. The steering lock-to-lock apparatus ofclaim 15 wherein said control compensator is a constant gain controlcompensator.
 17. The steering lock-to-lock apparatus of claim 15 furthercomprising: a high gain amplifier connected to a second input of saidswitch; said high gain amplifier receiving said signal corresponding toan absolute value of a road wheel torque signal when said switch isconnected to said second input.
 18. The steering lock-to-lock apparatusof claim 11 further comprising: a comparator connected to a controlinput of said switch; said comparator receiving a signal correspondingto an absolute value of a steering wheel angle; wherein when an absolutevalue of said steering wheel angle is less than a predetermined value,said switch is connected to a first input of said switch allowing saidsteering apparatus to move; wherein when said absolute value of saidsteering wheel angle is greater than or equal to said predeterminedvalue said switch is connected to a second input of switch causing saidsteering apparatus to be locked in position.
 19. The steeringlock-to-lock apparatus of claim 17 further comprising: a comparatorconnected to a control input of said switch; said comparator receiving asignal corresponding to an absolute value of a steering wheel angle;wherein when an absolute value of said steering wheel angle is less thana predetermined value, said switch is connected to said first input ofsaid switch allowing said steering apparatus to move; wherein when saidabsolute value of said steering wheel angle is greater than or equal tosaid predetermined value said switch is connected to said second inputof switch causing said steering apparatus to be locked in position. 20.The steering wheel lock-to-lock apparatus of claim 11 further comprisinga magnetorheological amplifier having an input and an output; said inputof said magnetorheological amplifier connected to an output of saidswitch; wherein said magnetorheological damper is responsive to anoutput signal received from said output of said magnetorheologicalamplifier.
 21. The steering lock-to-lock apparatus of claim 11, whereinsaid steering wheel is responsive to an output torque from saidmagnetorheological damper.
 22. The steering lock-to-lock apparatus ofclaim 11, wherein said switch is responsive to a road wheel torque froma road wheel system.
 23. A magnetorheological damper control for anautomotive steering control system, comprising: a motor amplifierreceiving a reference signal and generating a motor torque signal; amotor receiving an effective torque signal based on the sum of amagnetorheological torque signal, a driver action torque signal and saidmotor torque signal; said motor generating a road wheel rate signalbased on said effective torque signal; a magnetorheological damperreceiving said road wheel rate signal and an amplified control signalfrom a magnetorheological amplifier; said magnetorheological amplifierreceiving a control input signal and generating said amplified controlsignal based on said control input signal; said magnetorheologicaldamper generating said magnetorheological torque signal; and anintegrator receiving said road wheel rate signal and generating a roadwheel angle signal.
 24. The magnetorheological damper control of claim23 wherein said reference signal comprises a reference signal from asteering wheel controller.
 25. A steering wheel control system for avehicle, comprising: a first control subsystem comprising amagnetorheological damper, a steering wheel motor responsive to acontrolled input torque signal, said first control subsystem generatinga steering wheel rate signal; a second control subsystem comprising aposition loop compensator, a gain adjustable function element responsiveto an output from said position loop compensator, a motor amplifierreceiving an reference signal from said gain adjustable function elementand generating a motor torque and an integrator receiving said steeringwheel rate signal from said first control subsystem, said second controlsubsystem generating a steering wheel angle signal; and a third controlsubsystem comprising a steering ratio function element and a road wheelcontrol subsystem, said steering ratio function element receiving saidsteering wheel angle signal and generating a road wheel reference anglesignal, said road wheel control subsystem receiving said road wheelreference angle signal and generating a road wheel measurement torquesignal.
 26. The control system of claim 25 wherein said first controlsubsystem further comprises a magnetorheological control compensatorreceiving said road wheel measurement torque signal and generating acontrol reference signal, a magnetorheological amplifier receiving saidcontrol reference signal and generating an amplified control referencesignal.
 27. The control system of claim 26 wherein saidmagnetorheological damper receives said amplified control referencesignal, said steering wheel rate and generates a magnetorheologicaltorque.
 28. The control system of claim 27 wherein said control inputtorque signal is equal to the sum of said motor torque signal, saidmagnetorheological torque signal and a disturbance torque signal. 29.The control system of claim 25 wherein said position loop compensator isresponsive to the difference between a steering wheel reference anglesignal and said steering wheel angle signal.
 30. The control system ofclaim 25 wherein said gain adjustable function element receives a roadwheel torque signal.
 31. The control system of claim 25 wherein saidroad wheel control subsystem receives a road wheel disturbance torquesignal.
 32. The control system of claim 25 wherein said road wheelcontrol subsystem generates a road wheel angle signal.
 33. A method ofimproving steering feel in an automotive steer-by-wire control system,comprising: (a) sensing a steering wheel angle; (b) sensing a road wheeldynamic; (c) controlling a magnetorheological damper in response to saidsteering wheel angle and said road wheel dynamic; (d) controllingsteering feel in response to said magnetorheological damper.
 34. Themethod of improving steering feel in an automotive steer-by-wire controlsystem of claim 33, further comprising: (e) providing a road wheel angleto a road wheel system as a function of controlling saidmagnetorheological damper and said steering feel.
 35. The method ofimproving steering feel in an automotive steer-by-wire control system ofclaim 33 where (b) comprises sensing a road wheel torque.
 36. The methodof improving steering feel in an automotive steer-by-wire control systemof claim 33 where (c) comprises sensing a steering wheel referenceangle.
 37. The method of improving steering feel in an automotivesteer-by-wire control system of claim 34 where (e) comprises: sensing arotary rate of said magnetorheological damper; sensing a driverdisturbance torque from movement of said steering apparatus; andrepetitively calculating a road wheel angle in said computer based on:${\theta (s)} = {{\frac{M(s)}{s\left( {1 + {{M(s)}{N\left( {\omega {,\quad}\quad i_{{ref} - {mr}}} \right)}}} \right)}{\tau_{d}(s)}} - {\frac{K_{amp}{M(s)}}{s\left( {1 + {{M(s)}{N\left( {\omega,\quad i_{{ref} - {mr}}} \right)}}} \right)}{i_{ref}(s)}}}$

where M(s) represents a transfer function of a steering wheel motor andan assembly of said steering wheel motor, K_(amp) represents a gain of amotor amplifier, i_(ref-mr) represents an input control signal to saidmagnetorheological damper, i_(ref) represents an input reference signal,s represents a complex variable of any given point in a frequencydomain, ω represents a rotary rate of said magnetorheological damper,τ_(d) represents said driver torque and N(ω,i_(ref-mr))represents anon-linear transfer function of said magnetorheological damper.
 38. Amethod of locking a steering system, comprising: producing a steeringapparatus position; controlling a magnetorheological damper in responseto said steering apparatus position; and locking said steering apparatusin response to said controlling said magnetorheological damper.
 39. Themethod of locking a steering system of claim 38, wherein said producingsaid steering apparatus position, comprises: moving said steeringapparatus; and sensing said steering apparatus position produced by saidmoving steering apparatus.
 40. The method of locking a steering systemof claim 38, wherein said controlling a magnetorheological damper,comprises: comparing said steering apparatus position with apredetermined value where when said steering apparatus position is lessthan said predetermined value, said magnetorheological damper producesan output torque unlocking said steering apparatus; and when saidsteering apparatus position is greater than or equal to saidpredetermined value said magnetorheological damper produces an outputtorque locking said steering apparatus.
 41. The method of locking asteering system of claim 38, wherein said locking said steeringapparatus, comprises locking a steering wheel.